Energy Transfer in an Optically Pumped D2O Gas THz Laser

Abstract

We report on the mid-infrared (MIR) and terahertz (THz) wave spectra of D₂O gas pumped using a fundamental transverse mode transversely excited atmospheric CO₂ laser with an emission wavelength of 9.26 μm. We obtain MIR emission lines at center wavelengths of 9.262, 9.491, and 9.752 μm, which correspond to the vibrational-energy-level-transition lines of D₂O. We observe an intense THz stimulated Raman emission line of 385 μm and a weak cascade-transition line of 359 μm for transitions from rotational levels 4₂₂ to 4₁₃ and 4₁₃ to 4₀₄ in the first-excited vibration state of the D₂O molecule gas. We establish a four-energy-level system for modeling the laser kinetics of the dual-wavelength (385 and 359 μm) superradiation THz laser. For the optically pumped D₂O gas 385 μm THz laser, in considering the cavity effect and insertion loss of a THz cavity oscillator, an approximation treatment of the THz laser kinetics can be made based on a three-energy-level system.